The overall goal of the proposed research is to develop a quantitative molecular-level description for the adsorption of proteins at solid interfaces. Although numerous experimental studies of protein adsorption on various solid surfaces have been reported, a complete quantitative molecular picture is yet to emerge. Existing theoretical models do not account for the detailed molecular structure of the protein in the adsorption dynamics. In particular, the orientation of a protein at a solid interface, as well as its lateral mobility, is highly significant in influencing its behavior. The specific aims of this proposal are to: (1) Develop models for proteins that account for their shape and charge distribution and investigate the behavior of the models with Brownian dynamics simulation. (2) Develop Brownian dynamics code to simulate the model proteins accounting for protein-protein and protein surface interactions. (3) Examine the orientation of the adsorbed proteins as a function of surface coverage, ionic strength and temperature and the influence of the adsorption orientation on the kinetics of the process. (4) Understand the influence of lateral mobility on the adsorption kinetics and the structure of the adsorbed layer. (5) Investigate the molecular mechanism of lateral diffusion using a detailed molecular model. (6) Compare the predictions of the models with experimental data, which will allow us to refine the models or suggest new experiments. Protein adsorption plays a key role in many medical processes. For example, the performance of contact lenses and blood contacting devices is determined by the nature and the amount of the adsorbed proteins. A fundamental understanding of protein adsorption helps in the design of biocompatible surfaces for various medical applications.